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South Australia has imposed a range of new local COVID-19 restrictions in response to the growing number of virus cases around the country.

From midnight on Monday masks will be mandatory in high-risk settings, including aged care facilities and hospitals and will be highly recommended on public transport.

A new density arrangement of one person to every two square metres will be enforced in cafes, pubs, restaurants and other venues while private gatherings will be limited to 150 people.

People consuming food and drink at indoor venues must be seated.

Premier Steven Marshall said it was hoped the new measures would only be required for a week.

But he said the government had to act quickly given the potential for the rapid spread of the Delta variant of COVID-19.

"Given the nature of the rapid spread of the Delta variant we have no option but to take pre-emptive action to keep South Australians safe," the premier said.

"We have to be very vigilant at the moment."

The new measures follow SA's move on Sunday to close its border to Queensland, WA, the NT and the ACT after previously locking out travellers from NSW.

Chief Public Health Officer Nicola Spurrier said all the new restrictions and rules tried to balance the risk to health with the economic and social impact.

She said there were no new virus cases reported in SA on Monday, with all 29 miners from the Northern Territory, who were potentially exposed to the virus, returning negative results.

The workers were among 900 fly-in-fly-out personnel who recently left the Granites mine, north of Alice Springs, where one person tested positive last week.

Six virus cases have now been linked to the mine, including three in Darwin.

SA Health said the miners remained in isolation, along with their families.

© AAP 2021

NSW coach Brad Fittler has urged his side to capitalise on their dominance and push on to the most one-sided series result in State of Origin history following their game two destruction of Queensland.

The Blues cast aside an extraordinary build-up to the Suncorp Stadium clash, their backline again running rings around the Maroons in a series-clinching 26-0 victory on Sunday night.

Josh Addo-Carr scored twice, captain James Tedesco was instrumental at fullback and Latrell Mitchell bagged an intercept try as one of several big first-half plays that set the tone for the match.

It was the first time Queensland have been held scoreless in Brisbane and followed a record 50-6 thrashing of Paul Green's men in Townsville.

Now a cumulative scoreline of 76-6 leaves Fittler's side with wiggle room in July 14's third game to eclipse the previous-best 62-point differential NSW accrued in a 3-0 series victory in 2000.

The Maroons plucked a series win last season but the Blues have now made it three from the last four as they eye their own sustained period of dominance.

"That was a great team," coach Brad Fittler said of the 2000 side he captained.

"So (to be on track to replicate them) it's a bit of a sign of respect to each other ... (Sweeps) are not easy. They (Queensland) only had one (during an eight-year run).

"It can be (a period of dominance), but a lot of things have to work in your favour."

A last-minute injury to much-hyped Maroons debutant Reece Walsh on Saturday was quickly trumped by the eligibility concerns that saw his replacement Ronaldo Mulitalo withdrawn on game-day.

It certainly didn't bother the Blues though as they weathered an intense first 10 minutes then exploited a tiring Maroons pack who weren't helped by their disjointed backline.

NSW scored three tries and bombed another in a decisive 21-minute period to blow Queensland away then desperately snuffed out the Maroons' best efforts when their own offence dried up in the second half.

"It hurts a lot right now but we're going to have to shake it off (because) they're licking their lips for 3-0," Maroons captain Daly Cherry-Evans said.

"I just hope the silver lining tonight might be that it sparks something inside of us that kicks us into gear.

"It's tough enough they've won the series, let alone (potentially winning) 3-0."

The Maroons looked lost when they did get a peek at the Blues' line, their attack clunky and slow as halves Cherry-Evans and Cameron Munster struggled to create.

It cost them too, Valentine Holmes pushing a pass that found the fingertips of Mitchell, who raced almost 90 metres for a 12-0 lead.

It was Mitchell's third big play of an influential first half, the centre dragging Holmes back in goal to earn a repeat set and stripping Kyle Feldt in a play that led to Addo-Carr's first try.

With Queensland's exhausted forwards out on their feet or already benched, the floodgates were completely opened when Addo-Carr again streaked clear after 32 minutes.

He found Tom Trbojevic for an 18-0 lead, Cameron Murray blowing another golden chance in a one-sided first half.

In for the injured Harry Grant at hooker for Queensland, Andrew McCullough was replaced by Ben Hunt just before halftime while centre Dane Gagai missed seven first-half tackles.

Addo-Carr's second try sparked wild celebrations with 10 minutes to go as Queensland became just the fifth side in Origin history to be held scoreless.

© AAP 2021

Darwin and surrounding areas are in lockdown following five new COVID-19 cases linked to a gold mine in central Australia.

Chief Minister Michael Gunner says the outbreak represents the Northern Territory's biggest crisis since the beginning of the pandemic.

The lockdown started at 1pm Sunday after 900 workers left Newmont's Granites Mine about 540km northwest of Alice Springs, where a Victorian man had earlier tested positive.

About 400 fly-in-fly-out workers travelled in recent days to Brisbane and 250 flew to Perth, with 244 remaining in the NT.

NT authorities moved fast to track down those people who stayed but they were unable to find about 20 by Sunday morning.

It prompted Mr Gunner to order the Top End into lockdown.

There was a need to "assume the worst, assume they are positive and assume that there are exposure sites".

The 20 people have since been found and ordered to isolate but more cases are likely.

"Everything we see points to this being the highly-infectious Delta variant," Mr Gunner said.

"We are expecting more cases.

"There is a stronger chance that any new cases will have exposure sites which makes the job of tracing and testing much bigger."

Mr Gunner said one of the five positive cases had travelled to NSW. Another positive case has been identified in Queensland.

Two from the cohort are isolating at the mine in the Tanami Desert but would be evacuated to the Territory's Centre for National Resilience at Howard Springs.

The fifth case was a close contact of one of the mine workers, who lives in Palmerston south of Darwin. He tested positive to COVID-19 while in the Howard Springs centre.

Mr Gunner said the Palmerston case involved a 64-year-old employee of the mine who had travel by plane to Darwin on Friday.

He was picked up by his wife and went straight home to Palmerston.

His only other travel was to collect his adult daughter from her workplace and he did not leave the car. His wife and daughter had no additional movements.

When interviewed on Saturday, the man told contact tracers he was isolating at home with his wife and daughter and had developed symptoms.

From there, he was immediately tested and taken to the Centre for National Resilience.

Darwin, Palmerston and Litchfield local government areas - and the Wagait and Belyuen shires - entered a 48-hour lockdown with anyone leaving their home required to wear a face mask.

Residents are only permitted to leave home for medical treatment, to obtain essential goods and services, for work considered essential, one hour of exercise a day or to provide care.

© AAP 2021